The present invention relates to improvements in thermoformed plastic containers for food or other articles and particularly to latching structure for holding the lid and base of the container in closed condition.
Containers for food or other articles thermoformed from plastic material normally comprise a lid and base which may be hinged to each other or may be separate parts. In order to hold the lid and base of the container in closed condition, it is necessary that the lid and base have latching structure which can be manually opened and closed with relative ease. However, the structure should be capable of locking the container in closed condition to avoid accidental opening.
Various types of latching or locking structures have been proposed in the past. For example, cylindrical male and female locking elements have been proposed as disclosed in U.S. Pat. No. 4,576,330. Elongated rib structures comprising cooperating male and female elements have been proposed as disclosed in British Patent Specification 1,418,897 and in Canadian Patent 1,117,491. In the prior elongated rib structure locking elements the locking action has taken place on the long sides of the ribs. This required that the ribs be located in such a position on the container that both sides of the ribs are engageable by the cooperating male and female elements to provide the locking action.
It would be desirable to provide mating male and female rib elements where the locking takes place at the end of the ribs rather than along the sides of the ribs. This permits the latching structure to be located at various locations on the container and also provides for a more positive latching action while permitting ease of manual operation in opening and closing the latching structure on the container.